Valveless rock drill



I March 4, 1930.

VALVELESS ROCK DRILL L. W. GREVE Filed May 5. 1928 Patented Mar. 4, 19 30 coMrAnx-for' cnn i rnnnnngonro 1 vAnvnnnssnocxnnrnn Application enem a, 19 2s. Serial 1To. 274,82 5

The present invention is directedflto improvements in valveless rock drills. p

The primary object of theinvention is to provide a'device of this character so constructed that the shock incident to the piston hammer changing its working stroke will be absorbed in order thathth'e' drill can beheld I and operated with comparative comfort by the'drill runner. I I Another object of the invention is to provide a device of thistype constructed and arranged in such manner that. the rearward movement of the hammer will be cushioned by live pressure fluidzduring a portion of the rearward strokethereof.

Another objectof the invention is to provide. a drill of thiskind wherein the piston hammer will deliver a powerful working blow, the construction being extremely simfully described, claimed, and illustrated in the accompanying. drawing, in which g 1 tional view through the device.

ple, eflicient in operation, and which can be manufactured at a small cost.

With these and other objects in View, this invention resides in the novel features of construction, formation, 1 combination .and arrangement of parts to be hereinafter-more iThe figure represents 'a longitudinal "sec- Referring to the drawing; 1 designates a cylinder in which is formeda piston chamber 2 opening-at its rear end into a cushioning chamberB. The front end of the chamber 2 7 is closed, in this instance,'by the tappet case gand-in which is located the usual tappet 5.

The rear end'of the cushioning chamber?) is closed by. a bushing. 6 which has formed integral therewith a'sleeve 7 {said sleeveextending into the chamber 3; said bushing and sleeve constituting a relatively small rear piston chamber 8. The rear end of the piston chamber 8 opens, into the rear constant air chamber9 formed in the back head 10.. The rear wall of the chamber Sis-provided with a pocket 10,; the purpose of which will be later explained. Pressure fluid isconducted to the chamber 9 through the passage 11, the flow thereof being controlled by a suitable valve structure.

pressure"fluid itherefrom. Theexhaust port 25 is so located that some pressure built: up for cushioning-the rearlfl reciprocable'in'thelarge chamber 2 anda i I small elongated head 14 operable in the ,cham. her 8. These heads areconnected by I a re;

duces an annular groove 16.

duced neck '15, the presence of which prior, l

[The cylinderflwall' hasrformed-thereih'a. a Y

longitudinal passage 17 the rear endofwhich f LOUIS w. cnnvn'on cLEvE An OHIO, Assre von ro'rrrncnnvnnnnnnoox DRILL.

communicates with theforward endyof the nately opened and closed by the .head 13 dur; ing reciprocation thereof.

j Thecylinderwallisfuither brov id d I v Q a longitudinal passageway 20 which communicates with the front end of the chamber 2 through a port 21, and with the" chamber8 through a'port 22, the latter port beingalte'r- "nately opened and 01 the piston hammer.

ose d 'iby the head .14 of .Exten'ding' longitudi'nally through 1 the bushingfi and sleeve-.7 is a condu'it'i23, the forward end of which communicates with an annularchannel 24"formed in the wall of the piston chamber 8 adjacent its forward end.

The 'rear end of saidconduit opens intofthe chamber 9 and 1 is constantly supplied. with ward'lmovefment of the piston hammerwill pass therethrough to atmosphere. However, I

sufficient. pressure will be maintained in the chamber 3 to cushion the rearward movement of the piston. hammer due to the fact that as soon as the head 13 uncovers the port 19 pressure fluid will be admitted to said chamber.

' As-shownin full lines in the drawing, the

piston hammer is about to begin its rearward "stroke and is in such position that the pressure fluid from the constant air chamber '9 will rearwardly, andthe head 13 uncoversv the port 19, ressure fluid passes. through the of the head 13. As thepiston hammer moves passage :1 through the port 18 into the,

chamber 3 and builds up pressure therein sufficient to cushion and slow up the rearward movement of the piston hammer. In.

this manner the sudden shock incident to the change of stroke of the piston hammer from its forwardto rearward stroke is absorbed by the cushioning action of the fluid in the chamber 3 before pressure fluid is distributed for driving the piston hammer forwardly on its eworking stroke.

As the piston hammer continues. its rearward movement the annular groove 16 coincides with the channel 24 and the head 14;

cuts oil the flow of pressure fluid through the port 22 to the passageway 20. When the annular groove coincides with the channel 24 pressure fluid from the constant pressure chamber 9 flows through the conduit 23, into the channel 24, and from thence past the neck 15 to act against the rear face of the head 13, thus driving the piston hammer forwardly with considerable power to strike the tapet 5. p The pocket 10 will obviously aid in cushioning the rearward movement of the piston hammer at time when the rear end of the head V 14- enters the same.

That is claimed is:

A drill of the class described, comprising a cylinder having passages formed in its wall, said cylinder havinga relatively large piston chamber and a cushioning chamber communicating therewith, a bushing providing a small piston chamber fitted in the rear end of the cylinder, one of the passages connecting the 'large'chamber andcushioning chamber, apiston hammer including a large head and a small head operating,respectively, in the large and small chambers, 'means' for conducting pressure fluid tothe bushing, the small head controlling'the'flowof pressure fluid from the bushing through one of the passages to the frontand rear faces of the large head, said large head controllingthe flow of pressure fluid through the other passage to the cushioning'chamber' operating on the rear of said head.

In testimony whereof I afi'ix my signature.

c LOUIS WpGREVE. 

